1. Field of the Invention
The invention relates to a sealing device, referred to herein as a leaf seal, which uses a thin sheet or leaf to ensure fluid tightness between two zones of fluid flow. It is of use in particular with turbomachine nozzle rings to ensure fluid tightness between an aerodynamic flow path in which there is a hot gas flow and a chamber supplying air for cooling a nozzle ring.
2. Summary of the Prior Art
Leaf seals are often used to ensure fluid tightness between two adjacent structural elements of a turbomachine in which there is a considerable pressure difference between the structural elements.
When the structural elements are of annular shape, as in the case with many turbomachine elements, a number of curved leaf seals are used and arranged in contact with one another so as to form a substantially continuous annular seal between the structural elements.
The known leaf seals comprise a thin flexible leaf formed with an aperture in which a pin secured to one of the adjacent structural elements slides.
To retain the leaf in a sealing position the seal may also comprise, as described, for example, in French patent No. 2649463, a spring comprising a first part mounted on one of the structural elements and a second part mounted on the seal support pin. The problem with this seal is that leakages occur through the aperture in which the pin slides.
It is an object of the invention to solve this problem and to provide an effective leaf seal which is not permanently mounted on the structural elements, the seal comprising a pinless retaining system which is easy to demount and manufacture and which retains the seal stably in its operative sealing position.
To this end, the invention provides a leaf seal for ensuring fluid tightness between a first and a second structural element having a space therebetween, said leaf seal comprising at least one flexible sealing leaf disposed in a sealing position in said space between said first and said second structural elements, said sealing leaf having first and second contact generators bearing on said first and second structural elements respectively, and a retaining bracket having a first end bearing on said sealing leaf and a second end which is bent back and engaged in a groove provided in said second structural element in order to locate said sealing leaf axially and to retain said sealing leaf permanently in said sealing position by clamping said leaf between said retaining bracket and said first and second structural elements.
Preferably, the sealing leaf is retained radially in position by retaining means in the form of lateral lugs provided on the retaining bracket and lugs which are bent at right-angles at the lower end of the leaf and which engage under the lateral lugs of the bracket.
In the case in which the seal comprises at least two adjacent leaves placed edge to edge, the seal also comprises a flat cover strip or plate disposed between the leaves and the bracket so as to cover the joint between the two adjacent leaves.
Further preferred features and advantages of the invention will become apparent from the following description of the preferred embodiments, given by way of example only, with reference to the accompanying drawings.